1. Field of the Invention
The present invention relates generally to encoding and decoding schemes and data transmission and reception devices for wireless communication systems, and more particularly to facilitating the systems of short-range communication between stationary or mobile devices and mobile (including portable) devices, using an acoustic communication channel for data transfer over short distances.
2. Description of the Related Art
Encoding and data transfer apparatuses, used for different types of communication channels are widely known, and include a disassembler for disassembling an information object into data packets, wherein each packet is conveyed in a certain sequence to the error-correcting coding unit, the interleaver, the unit of control data addition.
The encoded packets are conveyed to the modulator, synchronization sequence addition unit and further to the encoder output for transmission through the communication channel. High noise immunity of data transfer is usually achieved by means of encoding with a high level of redundancy, enabling transmission of the objects with an increased probability of error-free reception in the communication channel with considerable interference, but causing a significant decrease in the object transmission speed on the other hand.
There are systems of information objects transfer by means of audible tones, including transceiver T (including a transmission apparatus) both in the receiving and transmitting section. Nonetheless, during the transmission, transceiver T1 includes a disassembler for disassembling an information object into data packets, each of which is conveyed to the encoder and the interleaver in a certain consequence. Furthermore, the transceiver T1 includes a modulator, where the converted packets are modulated by the audio signals and conveyed to transceiver 2 through the digital-to-analog converter and the loudspeaker. While reception at the analog-to-digital converter of transceiver 2, the audio signal received through the microphone is digitized, then is transferred successively to the synchronization unit, demodulator, deinterleaver, decoder, data restorer. At the same time, each incoming data packet is restored, the transmitted object is gradually received and its quality/integrity is determined. In case of losses transceiver T2 transmits a corresponding signal to transceiver T1, after conveying of the said signal, the new parameters of transmission through the acoustic communication channel are established (for example, power of the acoustic tone is increased) and the object is repeatedly transferred to transceiver T2. A drawback of such systems is the complexity of apparatuses in receiving and transmitting section, since a feedback mechanism is obligatory between the apparatuses in the receiving and transmitting sections (each of them must contain transceiver); slow response to the changing noise situation and, as a consequence, low rate of information objects transmission.
There also exist acoustic transmission systems, where the information object transmission speed is constant, does not take into account interference (acoustic) or environment (degree of noisiness of acoustic channel). Also, there is a feedback communication channel used for adjusting modulation type or speed of the error-correcting code.
The most relevant is a system of the acoustic data transmission without feedback, in which the transmission apparatus encodes the information object en bloc and cyclically repeats its transmission. The receiving apparatus in the receiving mode makes attempts to receive the encoded object until its error-free reception is achieved.
The drawback of the system is its inefficiency. In the case of at least one error during reception, repeated transmission is expected and the transmitted code and the audible tone parameters remain unchanged. Thus, during objects transmission, especially of a large amount of data, the possibility of erroneous reception increases drastically, and the transmission speed decreases and can not be optimal for the arbitrary signal to noise ratio in the communication channel. Therefore, an information object transmission either with high noise immunity (a lot of redundant (checking) data during object encoding) is necessary so that the error-free reception can be provided by means of one-two repetitions, which affects the speed, or increased transmission speed, in which case, noise increase in the communication channel adversely affects the noise immunity and the object may not be received at all.